The astronomical theory and data compared - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 293

Table 10.5. Durations required for the transition
from glacial to interglacial conditions.

Time period Duration of transition

( kybp ) (kyr)

18-11 7

135-130 5

246-242 4

341-334 7

431-426 5

540-529 11

630-626 4

741-738 3

796-788 8

are solar driven: some find SH insolation to be important, others find NH
insolation to be important, and at least one believes it is the combination of NH
and SH insolation that is important. The problem is that identifying the connec-
tion between ice core chronology and variable insolation (whether NH, SH, or
both) is a subjective process that depends mostly on the perception of the viewer.
Furthermore, as pointed out previously, the pattern of variability of peak solar
intensity in one hemisphere is indistinguishable from that for the length of
summer in the other hemisphere. Establishing a cause-effect relationship is
dicult, and too many scientists seem to have formed premature judgments based
on inadequate data. In several cases, authors have not adequately distinguished
between necessary and sucient. Solar patterns that occur with deglaciations may
occur when no deglaciation occurs. These analyses would be more palatable if
they were not so emphatic; a little humility would go a long way.
Kawamura (2009) pointed out that Figures 10.10 to 10.13 show that each of
the past four terminations occurred during an upswing in NH insolation and,
therefore, he concluded that NH insolation drives deglaciations and claims that
warming in Antarctica causes deglaciation are not valid. While it appears to be
true that deglaciations occurred during upswings in NH insolation, some of these
upswings were quite moderate in amplitude and larger upswings occurred at other
times that did not cause a deglaciation. Figure 10.9 shows the onsets of deglacia-
tion for the past nine terminations (from Rothlisberger et al., 2008) on the same
timeline as peak solar intensity at 65 N. It is impressive that all nine onsets of
deglaciation were associated with upswings in insolation. The problem with this is
that some of these upswings are quite small in amplitude. Why were there no